1,516 research outputs found
Risk bubbles and market instability
We discuss a simple model of correlated assets capturing the feedback effects induced by portfolio investment in the covariance dynamics. This model predicts an instability when the volume of investment exceeds a critical value. Close to the critical point the model exhibits dynamical correlations very similar to those observed in real markets. Maximum likelihood estimates of the model’s parameter for empirical data indeed confirms this conclusion. We show that this picture is confirmed by the empirical analysis for different choices of the time horizon
Independent Orbiter Assessment (IOA): Assessment of the extravehicular mobility unit, volume 1
The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA effort performed an independent analysis of the Extravehicular Mobility Unit (EMU) hardware and system, generating draft failure modes criticalities and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The IOA results were than compared to the most recent proposed Post 51-L NASA FMEA/CIL baseline. A resolution of each discrepancy from the comparison was provided through additional analysis as required. This report documents the results of that comparison for the Orbiter EMU hardware
Independent Orbiter Assessment (IOA): Analysis of the extravehicular mobility unit
The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items (PCIs). To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. This report documents the independent analysis results corresponding to the Extravehicular Mobility Unit (EMU) hardware. The EMU is an independent anthropomorphic system that provides environmental protection, mobility, life support, and communications for the Shuttle crewmember to perform Extravehicular Activity (EVA) in Earth orbit. Two EMUs are included on each baseline Orbiter mission, and consumables are provided for three two-man EVAs. The EMU consists of the Life Support System (LSS), Caution and Warning System (CWS), and the Space Suit Assembly (SSA). Each level of hardware was evaluated and analyzed for possible failure modes and effects. The majority of these PCIs are resultant from failures which cause loss of one or more primary functions: pressurization, oxygen delivery, environmental maintenance, and thermal maintenance. It should also be noted that the quantity of PCIs would significantly increase if the SOP were to be treated as an emergency system rather than as an unlike redundant element
The antitumor drug, 1,3-bis(2-chloroethyl)-1-nitroso-urea, inactivates human nicotinamide mononucleotide adenylyltransferase.
Nicotinamide mononucleotide (NMN) adenylyltransferase (EC 2.7.7.1) from human placenta is rapidly inactivated by 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). A similar inactivation is observed with other C- and N-nitroso compounds. The inactivation by BCNU is dependent on incubation time, temperature and BCNU concentration. Protective reagents for -SH groups, dithiothreitol and beta-mercaptoethanol, and the substrate NMN are very effective in protecting NMN adenylyltransferase from BCNU inactivation and in preserving its catalytic properties, while ATP is less efficient. Incubation of BCNU-inactivated and dialysed NMN adenylyltransferase with dithiothreitol results in a partial recovery of the enzymatic activity
Commissioning of the MEG II tracker system
The MEG experiment at the Paul Scherrer Institut (PSI) represents the state
of the art in the search for the charged Lepton Flavour Violating (cLFV) decay. With the phase 1, MEG set the new world best
upper limit on the \mbox{BR}(\mu^+ \rightarrow e^+ \gamma) < 4.2 \times
10^{-13} (90% C.L.). With the phase 2, MEG II, the experiment aims at reaching
a sensitivity enhancement of about one order of magnitude compared to the
previous MEG result. The new Cylindrical Drift CHamber (CDCH) is a key detector
for MEG II. CDCH is a low-mass single volume detector with high granularity: 9
layers of 192 drift cells, few mm wide, defined by wires in a
stereo configuration for longitudinal hit localization. The filling gas mixture
is Helium:Isobutane (90:10). The total radiation length is
\mbox{X}_0, thus minimizing the Multiple Coulomb Scattering (MCS)
contribution and allowing for a single-hit resolution m and an
angular and momentum resolutions of 6 mrad and 90 keV/c respectively. This
article presents the CDCH commissioning activities at PSI after the wiring
phase at INFN Lecce and the assembly phase at INFN Pisa. The endcaps
preparation, HV tests and conditioning of the chamber are described, aiming at
reaching the final stable working point. The integration into the MEG II
experimental apparatus is described, in view of the first data taking with
cosmic rays and beam during the 2018 and 2019 engineering runs. The
first gas gain results are also shown. A full engineering run with all the
upgraded detectors and the complete DAQ electronics is expected to start in
2020, followed by three years of physics data taking.Comment: 10 pages, 12 figures, 1 table, proceeding at INSTR'20 conference,
accepted for publication in JINS
Memory beyond memory in heart beating: an efficient way to detect pathological conditions
We study the long-range correlations of heartbeat fluctuations with the
method of diffusion entropy. We show that this method of analysis yields a
scaling parameter that apparently conflicts with the direct evaluation
of the distribution of times of sojourn in states with a given heartbeat
frequency. The strength of the memory responsible for this discrepancy is given
by a parameter , which is derived from real data. The
distribution of patients in the (, )-plane yields a neat
separation of the healthy from the congestive heart failure subjects.Comment: submitted to Physical Review Letters, 5 figure
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